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    <script>
        var num = 7;
        var str = "我爱您~~中国";
        //num > 5 为true   str.lenght >= num为true  所以true && true 
        console.log(num > 5 && str.length >= num); //true
        //num < 5 为false  str.lenght >= num为true  所以false && false
        console.log(num < 5 && str.length >= num); //false
        //num < 10为true   !true  
        console.log(!(num < 10)); //false
        //num < 10为true   str.length == num为true  true || true 为true 所以!true
        console.log(!(num < 10 || str.length == num)); //false
    </script>
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